The above mentioned type of respirators are used for supplying respiration gas for persons who have to work or stay in an atmosphere that is hazardous for breathing. The air to be inhaled is purified or freed from the pollutant via a filter, or respiration gas is supplied into the respirator from a bottle-type reservoir via a flexible tube. In the case of respirators with a filter, indicators are arranged on or in the filter, and they either indicate the depletion of the filter material or the breakthrough of pollutants, so that the user of the mask will be warned or is able to replace the filter in time. Even though monitoring of filter devices is eliminated in compressed-air respirators, it is just as important to monitor the full facepiece mask for sealed fitting on the face part of the mask user in order to recognize whether leaks, which make it possible for pollutant-loaded ambient air to enter the air to be inhaled, occur at the sealing edge. In this sense, the term "respiration connection" can be considered to denote both the filter connection and the tube connection for a compressed air-operated respirator or for the full facepiece mask itself.
In a prior-art full facepiece mask according to DE-PS 962,313, a colorimetric indicator is provided in the interior space of the mask, and it indicates the passage of harmful components from the environment into the interior space of the mask by a detection reagent arranged on a support changing its color in the presence of the pollutant being monitored. However, this prior-art mask has the disadvantage that it is dependent on the site of application of the indicator, insofar as passage due to leakage or depletion of the filter is indicated, depending on whether the air to be inhaled also flows past the indicator. The respiration air is routed, especially in respirators with inner half mask, such that passage openings with corresponding check valves, through which the air to be inhaled flows, are provided between the outer space of the mask and the inner space of the mask. In an air stream thus directed, the prior-art indicator is usually located in the flow shadow, and it permits only inaccurate indication of pollutant passing through at best.